Which disorder involves a slow, progressive loss of cognitive function that is irreversible?

The disorder characterized by a slow, progressive loss of cognitive function that is irreversible is dementia. Dementia is not a specific disease but a general term that encompasses various conditions, including Alzheimer's disease, vascular dementia, and frontotemporal dementia, among others. It primarily affects memory, thinking, and social abilities to the extent that it interferes with daily functioning.

The defining feature of dementia is its chronic and progressive nature, leading to a gradual decline in cognitive capabilities. Patients may initially experience mild memory issues, which can develop into significant impairments in areas such as language, problem-solving, and reasoning. As the condition advances, individuals may struggle with recognizing loved ones, managing daily tasks, and eventually may require full-time care.

In contrast, delirium is an acute, often reversible state of confusion typically resulting from medical conditions or medications and can fluctuate in severity; therefore, it does not describe a progressive cognitive decline. Amnestic disorder involves memory deficits primarily without the progressive cognitive decline seen in dementia. Acute stress reaction is a temporary response to a traumatic event and does not involve the gradual cognitive deterioration associated with dementia.